The invention relates generally to computed radiography (CR) systems and more particularly to a system and method for improving the scan speed and image quality in computed radiography systems.
Computed radiography systems employ imaging techniques that capture X-rays as they pass through an object to be imaged using an imaging plate coated with storage phosphors. The object to be imaged is typically exposed with X-rays, and a latent X-ray image is formed on the imaging plate. The storage phosphors on the imaging plate when stimulated with a low energy laser beam release visible light at locations where X-rays are absorbed. The light is then captured and converted into an electrical signal, which is subsequently converted to data that can be transmitted to remote systems or locations and displayed on laser-printed films or softcopy workstations and stored digitally.
Traditionally, computed radiography scanning techniques employ a continuously scanning laser beam that repeatedly scans the imaging plate in a horizontal direction while the imaging plate is slowly moved in an orthogonal direction thus scanning the entire plate surface. Ideally, the stimulated light from a given area of the phosphor would decay to zero immediately after the stimulating laser beam moves to the next pixel position. However, in practice, the decay time is small but finite. As the laser beam continuously scans the imaging plate, it sequentially exposes all pixels on the imaging plate. The light emitted by the entire plate is then typically collected by a global collection system that collects light emitted anywhere on the plate surface and then routes the light to a light detector. Thus, the detected signal is a combination of the desired pixel intensity and the decaying signal from the previously scanned pixels on a given row. Depending on the application, the contaminating old light may extend over 6-12 previously scanned pixels. This leads to a reduction in image quality and measurement accuracy.
An alternate scanning technique currently employed in computed radiography systems comprises stepping the scanning laser beam from left to right in discrete steps across the imaging plate. The scanning laser beam progresses to the next pixel in the imaging plate only when the light from the past pixel has decayed to a near zero value, thereby restricting the scanning velocity of the laser beam.
It would therefore be desirable to develop a scanning technique and improved computed radiography system that increase the scanning velocity and improve the image quality. In addition, it would be desirable to develop a technique and system that enable the measurement of a particular section of the imaging plate to be performed independently of the rate of decay of the previously exposed sections of the imaging plate.